In this study we examine the passage of a reform to in-vitro fertilization (IVF) procedures in Sweden in 2003. Following publication of medical evidence showing that pregnancy success rates could be maintained using single rather than multiple embryo transfers, the single embryo transfer (SET)...

The occurrence of twin births has been widely used as a natural experiment. With a focus upon the use of twin births for identification of causal effects in economics, this chapter provides a critical review of methods and results.